rather than only drivers attached later on. This involves a small amount of
code duplication with dev/fb/fbd.c, which will fixed later on.
Also improve performance of vt_blank() by making it not read from the
framebuffer unnecessarily.
o Forward termianl framebuffer ioctl to fbd.
o Forward terminal mmap request to fbd.
o Move inclusion of sys/conf.h to vt.h.
Sponsored by: The FreeBSD Foundation